Question

I have a quadratic equation struct, and I’d like to make it look nicer in the visual studio 2008 debugger. Here’s the struct:

struct QuadraticEquation
{
    float squareCoefficent; float linearCoefficent; float yIntersection; 
}

I’d like it to appear as a properly formatted equation in the debugger:

3.0x^2 - 1.3x + 6.5

Here’s the autoexp.dat preview script:

QuadraticEquation{
    preview
    (
        #if($c.squareCoefficent != 0.0f)
        (
            #($c.squareCoefficent, "x^2")
        )
        #if($c.linearCoefficent < 0.0f)
        (
            #(" - ", -$c.linearCoefficent, "x")            
        )
        #elif($c.linearCoefficent > 0.0f)
        (
            #(" + ", $c.linearCoefficent, "x")            
        )
        #if($c.yIntersection < 0.0f)
        (
            #(" - ", -$c.yIntersection)            
        )
        #elif($c.yIntersection > 0.0f)
        (
            #(" + ", $c.yIntersection)            
        )
    )
}

Pretty straight forward. But when I run the code, I get the following error message:

ERROR! Autoexp.dat:line(286) for 'QuadraticEquation': Failed to match ')' for preview/children rule

The line number corresponds to the second #if branch, that starts #if($c.linearCoefficent < 0.0f)...

If I remove everything except the square coefficent branch, it doesn’t error. If this means that I can’t have sequential #if blocks, how else could I do what I want here – without dropping into a dll?

Answer 1

I think you have to use nested #if‘s to achieve something like this. Check how std::complex<*> is done in the default autoexp.dat.

This will take a lot of typing to cover all possible combinations. Do you really need that? Maybe displaying it simply as a struct is good enough for practical purposes.